Sealing collar nut saves parts and assembly time

>Nut and bolt or stud fasteners are frequently required to lock and seal against liquids or gases. In these applications conventional fasteners can comprise several components and take time to assemble. But suppose you could have a reusable one-piece fastener that would dramatically reduce assembly time by providing a high performance seal in a single operation?

>These benefits can now be achieved in a new fastener through the design and incorporation of a moulded-in sealing ring which is threaded to ensure that there is no prevailing torque during run-down. Uniquely, because the seal ring thread form is in perfect synchronisation with the thread in the metal body of the fastener, rather than on its collar, the quality of seal is optimised. In effect a high quality seal is achieved both inside the thread as well as under the flange of the nut.

>The system is called Seal Lock and it has been developed by Bollhoff. Seal Lock has found success internationally in hydraulic and gas components where the prevention of leaks is critical and disassembly for servicing and repairs is routine. The fastener can be reused up to five times and has a smaller footprint making is suitable for use where space is at a premium.

>The embedded seal enables sealing and locking at higher compression and locking forces than conventional lock nuts with no loss of preload in accordance with property class 8. Metal to metal contact optimises the tightening torque to ensure strong and reliable joints. Manufactured in polyamide (PA11) the seal is resistant to oils and solvents and has a temperature service range of -40 to 110°C.

>Designed to ISO 4759 Product class A, Seal Lock is available in sizes M6 to M20 - coarse and fine threads - all of which are tested to DIN standards. Other sizes and application engineered fasteners can be developed to meet specific requirements. The seal itself can also be produced in other materials to meet specific performance criteria. Protective finishing options for the collar nut include CrVI-free zinc plated or phosphate surface coatings.

>Seal Lock sealing nuts save assembly time and realise optimal screwed connections without loss of preload force at minimum space requirements. They have proven reliable in many assemblies including power steering units, hydraulic pumps, fluid Injection pumps, gearboxes, transmission cases, air filters, pump enclosures, hydraulic lifting gear and hydrostatic gears.

>In particular, the Seal Lock has been used to seal and lock adjusting screws in the return chamber of a way valve block in a hydraulic control system, and to lock a set screw on the pressure-limiting valve inside toothed feed pumps. It has also been used as an O-ring and lock on the control lever axle for an aeroplane refuelling device.